The field of the present disclosure is infusion pumps and relates generally to systems, apparatuses, and methods for pumping or infusing volumes of medical fluids to a patient, typically via an intravenous route.
Infusion pumps are used to infuse drugs and liquids into patients, typically via intravenous lines. While some infusion pumps pump relatively large volumes, there is an emphasis in the industry for pumps with the capability of precisely delivering small controlled volumes of liquid. Here, the drugs pumped may be very critical to the patient, such as analgesics, anesthetics including opiates, anti-inflammatory agents, insulin, anti-spasmodic drugs, antibiotics, chemotherapy agents, cardiovascular drugs, and the like. Many of these drugs are needed in very low doses on a continuous basis, so that the patient receives a steady, reliable stream over a longer period of time, such as 0.1 ml per hour. Drug pulses may also be used, in which the dosage rate can be measured in terms of nanoliters or microliters per pulse or bolus. In any case, the accuracy of the pump is important to a successful outcome for the patient.
Some infusion pumps have, along the length of tubing, a pumping chamber having an inlet valve and an outlet valve. The infusion fluid is admitted into a length of tubing in the pumping chamber through an opened inlet valve and then isolated by occluding the tube by closing the inlet valve at an inlet of the pump chamber. The outlet valve is then opened and a pumping mechanism compresses the length of tubing in question to pump or expel the fluid from the pumping chamber and towards the patient. Since the inlet is blocked by the closed inlet valve, the liquid can only exit through the outlet of the pumping chamber, through an open outlet valve. The outlet valve is then closed, completing a single pumping cycle or stroke. The inlet valve and pumping mechanism are opened to permit additional fluid to enter the pumping chamber from a fluid source in a next stroke and so on.
The pumping mechanism can comprise a single pumping member that compresses the tube against a stationary block or platen. Alternatively, the pumping mechanism may comprise a plurality of pumping fingers or members that compress the tube in sequence. In this instance, particularly if there are sufficient pumping fingers, such that at least one is compressing the tube at all times, there may be no need for an inlet and/or outlet valve.
The accuracy of the overall infusion is dependent upon the accuracy of each pumping cycle. It is therefore important to know accurately the volume of fluid pumped with each pumping cycle and to know the volume of the entire infusion over time. The volume of each pumping cycle is dependent upon factors such as the tube's internal diameter and the tube's wall thickness. A problem arises due to the variability of internal diameter and wall thickness from tube to tube. This variability is due to, for example, manufacturing processes and tolerances. It would be helpful to provide an infusion pump capable of determining, or measuring the internal diameter and/or wall thickness of the specific IV tube being used for a specific infusion.